Struts is an Action framework and JSF is component framework.
Action Framework: Struts (both 1 and 2) are action frameworks. In essence they give you the ability to map URLs to activities and code on the back end. Here, the layout and workflow tends to be more page oriented. As a developer you tend to interact with the HTTP request cycle directly, though Struts 2 helps isolate at least the binding of the request data to the action implementation classes.
Action framework coders can have more control of the structure and presentation of URLs, since their systems are more intimately tied to them compared to a component framework.
Component Framework: In a component framework, artifacts that are rendered on the page are initially developed as individual components, much like in modern GUI "fat client" libraries. You have components, they have events, and your code is written to work with those events against the components. Most of the time, in mainstream development, your code is pretty much ignorant of the HTTP request cycle and processing.
JSF eliminated the need of Form Bean and DTO classes as it allows the use of same pojo class on all tiers of the application because of the Backing Bean.
In struts framework we can access the request and response objects directly, as in case of JSF we can access request and response objects indirectly.
Struts has a more sophisticated controller architecture than does JavaServer Faces technology. Struts is more sophisticated partly because the application developer can access the controller by creating an Action object that can integrate with the controller, whereas JavaServer Faces technology does not allow access to the controller.
In addition, the Struts controller can do things like access control on each Action based on user roles. This functionality is not provided by JavaServer Faces technology.
Struts frameworks is better for "web sites", site like this one, sites that focus on delivering content to the user. Where it's mostly a "read only" experience for the end user who is likely to want to bookmark things, come back to arbitrarily deep pages, etc.
JSF framework is better for CRUD screens, back office applications, lots of forms and controls, etc. Here, the workflow is more controlled. You tend to not get to a "detail" screen with going through the "list" screen or "header" screen first, for example.
struts validate full beans (validator.xml) jsf has a pluggable validator-mechanism
